#include <iostream>
using namespace std;

volatile int  count = 10;

constexpr int get_num()
{
    
    return 5;
}
int main(int argc, char **argv)
{
    constexpr int num = get_num();      //num已经被编译器认定为初始值为5

    int *p = const_cast<int *>(&num);   //未定义行为

    *p = 10;

    cout << num << endl;    //输出5
    
    return 0;
}